1) Field of the Invention
This invention is directed to a system and method of making parts and more specifically, a system and method of making parts using the manufacturing process of extrusion wherein the resulting parts have microstructures imparted on their surface.
2) Description of the Related Art
Extrusion is a manufacturing process that is used to create parts having a fixed cross-sectional profile. Extrusion material is pushed or drawn through an extrusion or drawings die of a desired cross-section. Extrusion can be used with extrusion material that is brittle since the extrusion material only encounters compressive and shear stresses. Extrusion also can produce finished parts with surface finish.
Extrusion may be a continuous process which can theoretically produce indefinitely long parts. In one form, extrusion produces semi-continuous parts resulting in a replication of virtually identical parts or parts having the same cross-section, but varying lengths. The extrusion process can be done with extrusion material that is hot or cold. Commonly extruded materials include metals, polymers, plastics, ceramics, concrete and foodstuffs.
Solid parts can be produced with a simple flat extrusion die. Hollow cavities within parts can be produced with a die having depth, beginning first with a shape profile that supports the center section. The die shape then internally changes along its length into the final shape, with the suspended center pieces supported from the back of the die. Mandrels can also be used to produce extruded parts having cavities.
Parts can also be effected by the drawings process. Drawing is a manufacturing process which uses tensile forces to stretch material. Generally, drawings is described as sheet drawing or wire, bar, and tube drawing. Sheet drawing involves deformation over a curved axis. Wire, bar, and tube drawing pulls material through a drawings die to reduce its diameter and increase its length. Drawing is usually done at room temperature, thus classified a cold working process, however it may be performed at elevated temperatures to hot work large wires, rods or hollow sections in order to reduce forces. Drawings can be used for metals and non-metals.
Under the current state of the art, the extrusion process (which includes drawing), generally produces a surface with a smooth or fine finish. It would be advantageous to be able to impart surface properties onto extrusion material during the extrusion process which results in the parts resulting from the extrusion process having certain physical properties.
Microfeatures placed on a part can provide for advantageous surface properties. By including a plurality of microfeatures on the surface of an object, other characteristics may be imparted to the object, such as increased hydrophobicity, hydrophilicity, self-cleaning ability, hydro-dynamics drag coefficients, aerodynamic drag coefficients, frictional properties, and optical effects. Superhydrophobic surfaces were first inspired by the characteristic water repellency of the lotus leaf.
Historically, microfeatures were applied to surfaces as coating, adhesive or chemical reaction and therefore are prone to wear of the surface. Over time the properties provided by the microstructures are lost. Further, the applications of a coating or adhesive would have to be added to the extrusion process and would not naturally be integrated into the extrusion process.
The information contained in PCT Patent Application: US09/43306, “Method of Manufacturing Microstructures”, filed on May 8, 2009; PCT Patent Application: US09/43307, “Flexible Microstructured Superhydrophobic Materials”, filed on May 8, 2009 and PCT Patent Application: US09/49565, “Casting Microstructures into Stiff and Durable Materials from a Flexible and Reusable Mold”, filed on Jul. 2, 2009 are incorporated by reference.
Additionally, there are attempts to increase the surface area of the fibers by using shapes that include “T”, “Y”, “Y” with a sphere at each distal end, “Y” with equal length legs, “Y” with rounded distal ends and an combination thereof. While these orifice shapes provide for fibers with increased surface area, they sacrifice strength when compared to a fiber with a circular cross-section.
Therefore, it is an object of this invention to provide an extruded filament using a die and extrusion process that resulted in parts having microfeatures.
It is another object of this invention to provide a filament which results in the filament including microfeatures imparting certain physical properties to the filament even when drawing.
It is another object of this invention to provide a filament that has microfeatures on its surface, such that these microfeatures are imparted on the filament thereby affecting the performance or properties of the filament.
It is another object of this invention to provide a filament with an increased surface area while maintaining generally a circular cross section.